Selecting system



SELECTING SYSTEM Filed Sept. 16, 1944 IOJ INVENTOR A. M SKELLETT A TTORNE V Patented May I, 1945 SELECTING SYSTEM Albert M. Skellett, Madison, N. 1., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application September 16, 1944, Serial No. 554,409

7 Claims.

This invention relates to selecting mechanisms and'more particularly to an improved selecting arrangement for use primarily in communication circuits, although it knot so limited and may find wide application as a selector for many purposes, either in its present or modifled form.

More specifically this is an improved selecting mechanism comprising a multianode electron beam tube having an improved control circuit. As presently arranged the tube and its control circuit may be considered as perform? ing the usual functions of the well-known startstop distributor in telegraph or teletypewriter systems. a

An object of this invention is the improvement of selectors.

A more particular object of this invention is the improvement of selectors in communication circuits.

A further object of this invention is the improvement of start-stop distributors in telegraph and teletypewriter systems.

A feature of this invention is an improved control circuit for a multianode electron beam tube.

Another feature of the invention is an oscillating circuit in which a transient voltage is developed to control themovement of the electron beam in a multianode beam tube.

Another feature of this invention is a gas tube in the input circuit of the mutianode electron beam tube to control the direction of certain of the pulses of a signal train to the input of the electron beam tube and to perform functions analogous to the stop functions in the usual rotary electromechanical start-stop distributor in a teletypewriter circuit.

These and other features of the invention will become apparent from the following description when read with reference to the drawing herein.

Refer now to the drawing.

Before proceeding with the detailed description of the operation of the circuit the condition of the circuit when idle will be described.

All of the apparatus shown on the drawing is assumed to be located at a teletypewriter receiving station. A telegraph channel IOI which may be of any of a number of forms extends to a distant receiving station either directly or through telegraph repeating equipment. The communicatio signals which are received over channel IOI comprise a train of seven signal impulses consisting of a, start signal impulse followed by a permutation code combination of five character or function determining signal impulses and a stop signal impulse. The start signal impulse is always a no-current impulse, each of the five following impulses is either a current or no-current impulse in accordance with the particular code combination and the lastimpulse is always a current impulse. Normally, when the channel is in condition for communication. both when it is idle and when it is in the so-called marking condition, direct current flows through conductor IN and through the left-hand winding of relay I02 to ground energizing relay I02. In this condition the armatures I03 and I04 are actuated to the positions shown. Armature I03 is disengaged from its contact I05. Armature I04 engages its contact I06 and contact I01 is open. Positive battery is connected through the right-hand winding of relay I02 to the anode of tube I08 which may be either a special gas fllled tube or a secondary emission tube, more fully described below. Negative battery I09 is connected through resistance I I0 to the grid of tube I08. Since contact I01, through which ground may be connected to the cathode of tube I08, is open, the tube I08 is not activated while the receiving circuit is awaiting the first or starting signal impulse.

Inductance III, condenser H2 and battery II3 are connected so that they may form an oscillating circuit under control of grounded ar-' mature I04 and contact I06 which is connected to the junction between the inductance and the condenser. The inductance coil III serves as the deflecting coil for the electron beam in tube II4. It is mounted adjacent and external to the envelope of multianode electron beam tube H4 and is so disposed with relation to the tube that the magnetic field of coil II'I invades the space within the envelope between the grid and anodes of the tube and controls the movement of the electron stream when emitted by the cathode by reason of the intensity of the field. The coil is so disposed with relation to the paths between the cathode and anodes that the magnetic field of coil .III is substantially'at right angles to the beam when the beam is directed at anodes I2l and I22.

There are six anodes in tube II4. These anodes are equally spaced i alignment preferably horizontally at the end of the tube opposite that in which the cathode and grid are located.

The grid may be of any of a number of usual types but is preferably 'of spiral type. In front of the six anodes is a screen having apertures in alignment with the six anodes.

Multianode electron beam tubes are well known in the art. Such tubes are described, tor instance, in. Patent 2,217,774 to A. M. Skellett, April 11, 1940, and a tube or this type suitably designed to operate to function as above described and to direct the control its flow is contemplated as the tube element II4 of this disclosure.

Negative battery. I I5 is connected through resistance IlIi to the grid 01 tube II4. Positive battery such as 1- is connected hrough the winding of a relay uch as II8 individually to each of the five upper anodes of tube II4, such as anode H9. The magnitude the negative potential H is such that while contact I05 remains open, no electron beam is established in tube II4 between the cathode and any of the anodes.

electron stream and While armature I04 is in engagement with contact I00, both the left-hand and right-hand terminals oi condenser II2 are grounded. Current flows from grounded positive battery I I3 through inductance coil III, contact I06 and armature I04 to ground. Inductance III is energized. The magnetic field or the inductance, as menuofied above, invades the envelope of the tube. For the waiting condition the magnitude of the magnetic field of inductance III is such that it would tend to direct a beam if emitted in a direction to, the left of the first anode I I9.

The" operation of the circuit will now be descri6ed in detail. It was explained that, while the circuit was awaiting the reception of the first or starting signal impulse of a signal train, current flows through conductor IOI energizing the left-hand winding of relay I02 and maintaining armatures I03 and I04 in the position in which they are shown on the drawing.

The first signal impulse of each train is always a no-current impulse. In responseto this the left-hand winding of relay I02 will be deenergized, releasing armatures I03 and I04. Contacts I05 and-I01 will be closed.

The closing of contact I01 grounds the cathode of gas tube I08 which is immediately activated. Current flows through the right-hand winding of relay I02 to the anode of tube I08, from the anode to the cathode and through contact I01 to ground. The right-hand winding of relay I02 will be energized. The efiect oi the current in the right-hand winding of relay I02 opposes the effect of current in its left-hand winding and is dominant over the efiect of the current in the left-hand winding when the current of succeeding current impulses 01 the signal train flows in the left-hand winding. When current signal impulses, among the following train of signal impulses for a particular permutation code combination, flow through the lefthand winding they tend to actuate the armatures I03 and I04 to the positions in which they are shown on the drawing, but since the effect or the current in the right-hand winding of relay I02 is dominant, armatures tained in engagement with contacts I05 and I01. After contact I05 closes, the circuit incoming from conductor MI is connected through a parallelbranch which extends through armature I03, contact I05, and condenser I25, which connects to the junction between the top terminal of resistance IIS and the grid of tube II4.

When armature I03 is released in response to the reception or the first or starting pulse which,

contact I00, by disconnecting ground from the left-hand terminal of the condenser, permits the condenser to start charging and initiates the first portion or an oscillating voltage in the oscillating circuit to tend to deflect the beam toward the right. The time of this portion of an oscillation and the magnitude or the voltage and conse- "quently the rate or movement of the beam are controlled by a choice of constants of the inductance III, the condenser H2 and the voltage II3 so that the period of the swing or the beam is substantially equal to the duration of a signal train minus the time of release and reoperation of relay I02. Those of the elements of the signal train following the no-current start pulse which are current elements will effect a change of potential between the grid or tube H4 and ground so as to cause the emission of an electron beam in tube II4 which will be directed at a particular anode corresponding in position to the position or the particular current signal element in the train. When a signal element of a particular permutation combination is a no-current element, no beam is emitted. Each of the relays connected to an anode upon which a beam impinges will operate. Each relay, such as I28, which operates establishes a circuit from battery through a closed contact on the relay such as I32, and through the winding of a solenoid such as I31 to ground.

Each solenoid which is operated actuates a bar such as I40 to the right. The bar I40 is connected at its left-hand end by means of a pin I, to the right-hand end of the link bar I42, the left-hand end of which is attached by means of a pin I43 to the right-hand end or a lever I44, which is arranged substantially at right angles to the link bar I42. The lever I44 is rotatable in a limited are about the vertical fulcrum I45.

I03 and I04 will be mainas has been explained in the foregoing, is a no- The lever I44 is attached at its left-hand end to a permutation code selecting vane which is normally actuated to the right by spring I41. When the solenoid is actuated, the vane I46 is actuated to the left against the tension of spring I41. Each of the other relays controls a particular vane corresponding to vane I46 in a similar manner. In response to the reception of a particular code combination the vanes, such as I46, will be set in such position that they will permit the entrance of a particular selecting bar such as I48 to effect a particular selection corresponding to the code combination. The relays are made slow to release. No relay releases until a selection is eftected.

It was explained above that the seventh or last signal element of each signal train is always a current signal element. In response to this a beam will always be directed at anode I24. Current thereupon flows from positive battery I49 through resistance I50 and from anode I24 to the cathode of tube II4 which is grounded. A circuit which in effect is a potentiometer may be traced from positive battery I49 through resistance I50, conductor I5I, condenser I52 and resistance IIO to negative battery I09.

The grid of gas tube I08 is connected to a point in this potentiometer circuit between condensers I52 and resistance IIO. Tube I08 may be either a special gas tube with a closed grid such as is described in Patent 2,113,392 to Sydney N. Baruch, April 5, 1938, or it may be a s'o-called secondary emission tube such as is described in Patent 2,293,177 to A. M. Skellett, August 18, 1942. Such tubes while having certain of the H4. The disengagement o1 armature I04 from u characteristics of trigger tubes also have the potential is impressed between the grid of tube device for establishing conditions tending to direct an electron beam at a particular anode in 7 said distributor at aflrst time, and means di- IM and ground. As a result of this. tube "I8 is inactivated. The right-hand winding of relay I2 is thereupon deenergized.

Since the seventh or stop pulse is a current pulse, the left-hand winding of relay. I02 is energized and as soon as the right-hand winding of relay III loses control, the armatures I" and I will again be actuated to the positions indicated.

Selecting bar I48 is withdrawn under control of apparatus (not shown) forming part of the teletypewriter receiver which is well known in the art. Vanes I46 are restored to their original positions by the springs such as I". The mechanism is then ready 101' the reception of the succeeding combination.

What is claimed is:

1. A multianode electron beam tube, an input v circuit connected to said tube, means directly responsive to said input circuit for controlling changes in the position of the beam in said tube, said means comprising a beam deflecting inductance coil connected to a capacitance to form an oscillating circuit, and means connected to said input circuit responsive to the reception of a signal impulse for generating a variable voltage in said oscillating circuit to control the movement of said beam.

2. A multianode electron beam tube, an input circuit connected to said tube, means in said input circuit for controlling changes in the position of the beam in said tube, said means comprising a beam deflecting inductance coil connected to a capacitance to form an oscillating circuit, means connected to said input circuitresponsive to the reception of a signal impulse for generating a variable voltage in said oscillating circuit to control the movement of said beam, an electron discharge device connected to said input circuit, and means connected to said device for controlling said oscillating circuit.

3. A teletypewriter signal receiving circuit, a telegraph signal receiving relay connected to the input of a multianode electron beam tube signal distributor in said circuit, a beam deflecting device connected to said distributor, said device consisting of a deflecting inductance coil. a condenser and a battery, means connected to said rectlv responsive to a signal impressed on said relay for controlling said device to direct the beam in said tube at other anodes in said tube at asecond time.-

4. A telegraph channel connected to a'teletypewriter receiving circuit for receiving a train of signal impulses followed by a stop signal impulse, a multianode electron beam tube in said circuit, means in said circuit responsive to the reception of the first signal of said train for connecting said channel to the input of said tube and directing the succeeding signals of said train to the input of said tube, means also in said circuit for directing an electron beam at a particular anode in said tube in response to the reception of said stop signal impulse by said circuit, and means comprising a second tube in said circuit responsive to the impinging of said beam on said particular anode for disconnecting said channel from the input of said electron beam tube.

5. A telegraph channel, a multianode electron beam tube, a telegraph signal receiving device, means responsive to the reception of the first of a train of signals by said device for connecting said channel to the input. of said tube, and means responsive to the reception of the last ofa train of signals by said tube for disconnecting said channel from said input.

6. A telegraph channel connected to a telegraph signal receiving device, a multianode electron beam tube, a beam deflecting coil adjacent said tube, means responsive to the reception from said channel by said device of the first of a train of telegraph signal impulses for impressing a transient voltage on said coil to control the direction of beams emitted by said tube, and other means responsive to the reception of said first impulse for directing succeeding impulses of said train to the input of said tube.

7. A start-stop permutation code telegraph receiving circuit comprising a multianode electron beam distributor tube, a beam deflector for said tube including means responsive to a start signal impulse for generating a transient beam defleeting voltage, anda beam'restorer for said tube comprising means responsive to a stop signal impulse for generating a flxed beam directins voltage.

- ALBERT M. SKELLETI. 

